The objective of the study reported here was to evaluate the effects of dexamethasone on physiological changes and productive performances in broilers. Broilers were divided into seven groups and received dexamethasone at 0 (control group), 1, 2, 3, 4, 5 and 6 mg kg-1 in their diets. Percentage of heterophils, lymphocytes, heteropil/ lymphocyte ratio, hemoglobin concentration, packed cell volume, total white blood cell count, body temperature, respiratory rate and productive performances (feed intake, average daily gain, feed conversion rate and body weight) of broilers were investigated on days 1, 7, 14 and 21 of the experimental period. The results revealed the following information: Heterophil, heterophil/lymphocyte ratio, total white blood cell count, body temperature, respiratory rate, packed cell volume and feed intake of broilers increased (p<0.05). On the other hand, lymphocyte, hemoglobin, average daily gain and body weight of broiler decreased (p<0.05). The results of this study indicated that synthetic glucocorticoid, dexamethasone had many effects on broilers like internal glucocorticoid. Side effects of dexamethasone to broilers were increased body temperature and respiratory rate and reduced growth rate even if feed intake of those chickens increased.